/Engine/Plugins/FX/Niagara/Source/Niagara/Classes/NiagaraDataInterfaceRW.h
For data interfaces that support iteration on the GPU we need to be able to get the 'real' element count as known only by the GPU The dispatch will use the CPU count, which is potentially an over-estimation, and the value inside the buffer will be used to clip instances that are not valid
virtual uint32 GetGPUInstanceCountOffset ( [FNiagaraSystemInstanceID](API\Plugins\NiagaraCore\FNiagaraSystemInstanceID) SystemInstanceID ) const